The problem is getting the races in and out of the steering knuckle, I haven't even attempted it, but if you take the bearings out, clean off the races and see if they're scratched or anything. If they're not id just put the new bearings in with the old races still in place.. if they have any scuffs or scratches you really need to change them tho. They can be really tiny scratches and still cause problems so look close.

Also the outer races are easy as can be, the inners are the ones that have issues coming off the inner hub.

If the Dimensions and specs are the same it shouldn't be a big deal, its not like your putting a new bearing in that has a different angle. I could see a problem with that, but since their all the same for an aspire it shouldn't be an issue unless the old races are worn.

I've been driving for about 3k miles on mixed races/bearings and haven't had any issues.

Bearings are sold in sets to fit a tolerance. Even if you have the most expensive grinding machines in the world you won't ever hold parts to the same tolerance every time. Set matched parts are parts that are tested together to meet a certain tolerance. As bad as our wheel bearings can be, why make the situation even more dicey when all you need is a punch and 5 extra minutes to pop the races out and the new ones in? especially if you aren't using the same manufacturer from bearing to bearing.

I love aspire wheel bearings lol, they're so simple and soo much cheaper than having to buy a 70$-140$ hub and bearing assembly lol. They remind me of the skateboards I had as a teenager, I'm still holding out hope for someday finding some abec 7's that'll fit on so my car will roll for dayssss..